Some important characteristics of Spirulina subsalsa var. crassior virieux have been investigated in this article. At the 36 degrees C, the growth rate K of this alga is 0.18 and the yield as high as 48.4 g/m(2)/d (dry wt). In practice, a yield with 17.7 g/m(2)/d was reached by mass culture outdoors in the natural conditions of Hangzhou, China. The protein content of this alga was over 50.30% in its dry matter. The composition and content of its amino acids and superoxide dismutase were analyzed. The results indicate that the Spirulina subsalsa var. is a promising thermophilic species for algal protein production.